Generally, in a gas turbine, a structure is frequently used in which in order to lock circumferential movement of a shroud segment, holes are formed in some circumferential portions of the shroud segment and turbine casing and the shroud segment is fixed to the turbine casing by inserting pins into the holes.
The pins fixing the shroud segment and the turbine casing are referred to as shroud lock pins. The shroud lock pins are inserted into shroud lock pin holes, passing through the turbine casing, from the outside of the turbine casing and lock the circumferential movement of the shroud casing and the turbine casing.
The shroud lock pin holes which pass through the turbine casing and into which the shroud lock pins are inserted have covers provided by tapered threads in order that the shroud lock pins are prevented from coming out of the holes or gas inside the turbine casing is prevented from leaking out of the turbine casing due to a difference in internal and external pressure of the turbine casing. The use of the tapered threads causes axial force of the threads to act in radial directions of the threads due to wedge effects of the tapered threads, thus making it possible to prevent the gas inside the turbine casing from leaking out of the turbine casing.
Incidentally, Patent Literatures 1 and 2 are listed as prior art literatures relating to the tapered threads.